Qiang W.,China University of Mining and Technology | Yuanzhang L.,China University of Mining and Technology | Yuanzhang L.,Beijing Institute of Hydrogeology and Engineering Geology | Liu Y.,Institute of Hydrogeology and Environmental GeologyMine Water and the Environment | Year: 2011

The excessive mining for underground water is the main reason inducing the land subsidence in Beijing, while, increasing of load brought by the urban construction aggravate the local land subsidence in a certain degree. As an international metropolis, the problems of land subsidence that caused by urban construction are becoming increasingly highlights, so revealing the relationship between regional load increase and the response of land subsidence also becomes one of the key problems in the land subsidence research field. In order to analyze the relationship between the load changes in construction and the land subsidence quantitatively, the present study selected the TM remote sensing image covering Beijing plain and used Erdas Modeler tool to invert the index based on building site (IBI), acquired the spatial and temporal change information in research area further; Based on results monitored by PS-InSAR (permanent scatterer interferometry) and IBI index method, and combined with the GIS spatial analysis method in the view of pixels in different scales, this paper analyzes the correlation between typical area load change and land subsidence, The conclusions show that there is a positive correlation between the density of load and the homogeneity of subsidence, especially in area which has a high sedimentation rate. Owing to such characteristics as the complexity and hysteretic nature of soil and geological structure, it is not obvious that the land subsidence caused by the increase of load in a short period. But with the increasing of local land load made by high density buildings and additional settlement of each monomer building superposed with each other, regional land subsidence is still a question that cannot be ignored and needs long-term systematic research and discussion.

Increasing of load brought by the urban construction aggravate the local land subsidence. As an international metropolis, land subsidence that caused by urban construction are becoming highlight increasingly in Beijing, China, so revealing the relationship between regional load increase and land subsidence also becomes a key problem. TM remote sensing image covering Beijing plain were selected and Erdas Modeler tool was used to calculate the index basing on building site (IBI), acquiring spatial and temporal change information of build-up area. Basing on deformation information monitored by PS-InSAR (permanent scatterer interferometry) technology and IBI index, combining with GIS spatial analysis method in the three different sampling ranges, the correlation between InSAR annual subsidence rate and IBI index was analyzed. The conclusions show that there is positive correlation between load density and uneven settlement, the higher settlement rate, the higher spearman rank correlation coefficient. Compared to the static load, the impact of combined dynamic and static load to land subsidence is more obvious. It is not obvious for the influence to land subsidence caused by the increase of load in a short period.

Excessive artificial extraction of groundwater has caused the continuous decline of groundwater levels and, as a result, triggered a large area of land subsidence. To avoid a wider range of land subsidence, the authors used the clay layer thickness, the drawdown rate of groundwater level and groundwater exploitation as three impact factors to carry out studies. In accordance with their respective extent of impact, the impact factor weights were determined, the overlay method in GIS was used to divide land subsidence into susceptibility zoning. In combination with water resource allocation of South-to-North water transfer, this paper has proposed the control measures on land subsidence, thus providing a scientific basis for layout optimization of groundwater exploitation and land subsidence.

The organic pollution of the groundwater is increasingly deteriorating. The south-east suburb of Beijing is selected as the study area. To determine the pollution pathway and trend, groundwater dynamic monitoring, investigation of pollution sources and the analysis of the characteristics of organic pollution of groundwater were carried out. The data of groundwater dynamic monitoring show that the main contaminant compounds are the chlorinated hydrocarbon (1, 2-DCA, CF, 12-DCP) and monocyclic aromatics hydrocarbon (benzene, toluene, ethylbenzene, xylene), among which 1, 2-DCA and benzene are the top two most serious contaminants. The organic contamination is characterized by punctate distribution and limited scope. Aimed to identify the source of the organic contamination in the groundwater, the surface water, soil and air have all been sampled for investigation. It is found that the source of monocyclic aromatic hydrocarbon contamination is chemical industry, while the source of chlorinated hydrocarbon contamination is surface water infiltration and reclaimed water irrigation. Combined analysis of concentration change regularity of 1, 2-DCA and benzene, hydrogeological condition, pollution sources and the characteristics of organic contaminations in shallow groundwater, demonstrates that the type of the pathway of chlorinated hydrocarbon and monocyclic aromatics hydrocarbon in the shallow groundwater are continuous-intermittent infiltration and intermittent infiltration respectively. The study facilitates the future theory and practice of protection and control of organic pollution.